Choke control for carburetor



Jan. 11, 1966 T. M. BALL 3,228,666

CHOKE CONTROL FOR CARBURETOR Filed Dec. 21, 1961 3 Sheets-Sheet 1 INVENTOR. 7%0 7774s M5477,

I TTaw/vr/g Jan. 11, 1966 T, BALL CHOKE CONTROL FOR CARBURETOR 3 Sheets-Sheet 2 Filed Dec. 21, 1961 INVENTOR. 77907774: /%,3d//

Jan. 11, 1966 1'. M. BALL CHOKE CONTROL FOR CARBURETOR 3 Sheets-Sheet 5 Filed Dec. 21, 1961 INVENTOR. 7%077746' )ZZd/Z /awww/ 9L Nam United States Patent 3,228,666 CHDKE CONTROL FOR CARBURETOR Thomas M. Bali, Bloomfield Hills, Mich, assign-or to Chrysler Corporation, Highland Park, Mich, a corporation of Delaware Filed Dec. 21, 1961, Scr. No. 161,189 3 Claims. (Cl. 26139) This invention relates to improvements in the automatic control of a carburetor for an .internal combustion engine and has for an important object the provision of improved control means for the conventional unbalanced choke blade effective to prevent stalling of the engine immediately after it has been started.

Occasionally when an automotive engine is initially started, a rush of inlet air blows the choke blade open surliciently to cause the engine to stall, particularly during unfavorable weather conditions. It is accordingly another object of the invention to provide improved simple and economical means which is highly effective to enable limited opening of the choke during and immediately after starting only, so as to prevent stalling, and which allow-s normal choke opera-tion after the engine has been started and the throttle has once been opened beyond the idle operating condition.

It is considered desirable to provide an automatic carburetor which will enable rapid engine starting merely by closing the starting motor circuit and without supplemental manual operation of the throttle. Such operation is often referred to as cam starting ecause the usual fast idle cam and cooperating thermostatic control are employed to maintain the throttle in the proper starting position. During cam starting the throttle will be at an idle position, such that the engine is especially susceptible to stalling in consequence of a surge of cold inlet air immediately after being started. Another object is therefore to provide improved automatic control means of the above character which is particularly adapted for cam starting, so as to limit the initial choke opening during and immediately after starting only, without interfering with normal choke operation at other times.

Still another objec is to provide a modified automatic control of the above character which is adapted for use in throttle starting wherein the throttle is open apprecia'oly beyond the normal idle operating position during starting.

Other obiects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

FIGURE 1 is a fragmentary and generaliy schematic view of a carburetor embodying the present invention, portions being broken away to illustrate details of corn struction, the choke blade being shown in the starting position.

FIGURE 2 is a view similar to FIGURE 1, the chol e blade in an idle opera-ting position.

FIGURE 3 is a view similar to FIGURE 1, a modification.

FIGURE 4 is a view similar to FIGURE 1, another modification.

FIGURE 5 is a view similar to FiGURE 4, illustrating the choke blade in the idle operating position.

FIGURE 6 is a view similar to FIGURE 1, showing still another modification.

FIGURE 7 is a View similar to FIGURE 6, but showing the choke blade in the idle operating position.

it is to be understood that the invention is not limited in .its application to the details of construction and arshowing showing showing "ice .rangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Referring to the drawings, particularly FIGURES 1 and 32, an embodiment of the present invention is illustrated by way of example comprising a carburetor for an automobile engine, the carburetor including a body 10 having the customary air inlet induction conduit 11. An unbalanced choke blade or valve 12 is secured to a rotatable shaft 13 journalled at opposite ends in the body 16. The blade 12 is pivotal with shaft 13 and is located in the upper portion of conduit 11 in accordance with conventional practice. A throttle valve 14 secured to a rotatable shaft 15 journalled at opposite ends in the body 10 is provided at a downstream location of the conduit 11.

Suitably located within a portion of the engine so as to be responsive to an operating temperature thereof is a spiral bi-metallic thermostat spring 16 having a fixed end 1'] secured to a fixed spindle 18. A swinging arm 19 pivotal on spindle 18 has an outer swinging and pivotally connected at 2t) to the lower end of an operating link 21. A free end 22 of thermostat 16 is engaged with arm 1% at the region of the connection 2% so as to urge arm 19 counterclockwise with progressively increasing force as the temperature decreases. The upper end of link 21 is pivotally connected at 23 to the swinging end of a crank arm 24 keyed to the choke shaft 13.

Keyed to the throttle shaft 15 is a throttle control lever 25 having one swinging end pivotally connected at 2t; with a personally actuated throttle link 27. The other end of lever 25 is provided with a threaded boss 23 having an adjustable idle control screw or cam follower 29 screwed therein. The inner end of screw 29 is adapted to engage a stepped cam surface 30 of a fast idle cam 31 when the latter .is in a predetermined cold idle operating position as described below. The cam 31 is keyed to a rotatable axial stub 32 journalled on the body It} and is provided with a counterweight portion 33 effective to urge clockwise rotation of cam 31 by gravity force toward a warm operating position.

Throttle lever 25 is normally urged clockwise toward the closed or idle position illustrated in FIGURES 1 and 2 by a customary throttle return spring 27a schematically illustrated under tension between a projection 25a of lever 25 and a fixed portion 27b of the engine. Foot pedal actuation of shaft 27 is effective to swing lever 25 counterclockwise to open'the throttle 14.

Upon closing movement of choke valve 12, the fast idle cam 31 is swung counterclockwise to the cold position by means of a link 34 having an upper end pivotally connected at 35 to a crank arm 36 keyed to shaft 13. The lower end of link 34 terminates in an extension 37 which projects in a direction parallel to the pivot axis of cam 31 through a lost motion slot 38 to complete a lost motion pivotal connection between link 34 and cam 31. An arcuate slot 38 is formed within the counterweight portion 33 concentrically with the pivot axis of cam 31 to enable opening movement of choke valve 12 independently of movement of cam 31, as described below, by virtue of extension 37 riding within groove 38. Extending radially within cam 31 and intersecting slot 38 is a movement limiting notch 39 arranged to receive extension 37 when cam 31 is in the cold position shown, FIGURE 1, thereby to limit opening movement of choke valve 12. As is apparent, the link 34 is provided with a lost motion connection with cam 31 by reason of the extension 37, slot 38 and notch 39.

In order to render the position of choke valve 12 responsive to the pressure in conduit 11 downstream of throttle valve 14, a vacuum cylinder 40 formed integrally with body contains a reciprocable piston 41 therein, see also FIGURE 6 and 7, pivotally connected at 42 to one end of a dog-leg link 43. The other end of the latter link is pivotally connected at 44 to the outer end of a projection 45 secured to valve 12 so as to swing the latter in a clockwise opening movement upon rightward movement of piston 41. The right end of cylinder 40 is connected by means of duct 46 with induction conduit 11 at a location downstream of throttle valve 14, FIGURES 2 and 7, thereby to urge opening of choke 12 against the force of thermostat spring 16 when the pressure downstream of throttle valve 14 is low, i.e. during engine idling.

During operation of the structure described, when screw 29 is in contact with the stepped cam surface 30, the frictional contact between screw 29 and surface 3% resulting from the tension of spring 27a is sufficient to prevent.

pivotal movement of cam 31 in consequence of the normal forces acting thereon, such as the forces resulting from counterweight 33, thermostat coil 16, piston 41, or the downwardly flowing air in conduit 11 acting on the unbalanced blade 12. In consequence, when the carburetor parts are in the cold position illustrated in FIG- URE 1 and the cold engine is initially started, opening of the unbalanced choke blade 12 by the initial surge of.cold inlet air in conduit 11 will be limited to a predetermined extent, as for example approximately 10, by downward movement of extension 37 into notch 39.

During this starting operation, the throttle 14 will be maintained in a fast idle position by reason of screw 29 engaging the fast idle step of the cam surface 30, FIG- URE 1. At the fast idle position, throttle 14 is cracked slightly open as illustrated in FIGURE 1, so that the engine will idle effectively in the cold condition. Thereafter, when throttle valve 14 is opened from the fast idle position to accelerate the-engine, the frictional engagement between screw 29 and cam surface 30 will be released to enable opening of choke valve 12 to the usual operating condition. By this time, the danger of engine stalling will have passed, because the stalling tendency described occurs only in the first two or threeseconds of engine operation.

After the throttle 14 has been initially opened from the starting position of FIGURE 1 to enable opening of choke valve 12 to a running position, if the throttle 14-and screw 24 are then returned to a cold idle position soas to engage one of the lesser steps of cam surface 30, the cam 31 will be locked against swinging movement as aforesaid by virtue of its frictional contact with screw 29. However in this instance, the cam 31 will now be in position to receive extension 37 within slot 38.. Thus if the engine is allowed to run at idle for sutficient timeto relax the closing force of thermostat spring 16 as a result of warming of the engine, choke valve 12 will be free to open by virtue of movement of extension 37 along slot 38.

If the engine is operated in the warm condition under load and is then turned off and allowed to cool, choke valve 12 will be locked against return movement to the closed position by contact between fast idle cam 31 and screw 29. Accordingly, in order to return the carburetor mechanism to the position illustrated in FIGURE 1, throtle 14 must first be opened to release the engagement between cam 31 and screw 29 thereby to enable thermostat spring 16'to return choke valve 12 and cam 31 to the position of FIGURE 1. Thereafter upon closing of throttle 14, screw 29 will engage the cold starting step of cam surface 30 as illustrated in FIGURE 1.

FIGURE 3 illustrates a modification of the present invention wherein the basic carburetor structure is the same as in FIGURES 1 and 2, except that notch 39 is eliminated and a spring finger 47 engages extension 37 under tension to resist clockwise opening movement of choke valve 12. A fixed end. 43 of finger'47 is secured to the pivotal axial stub 32 of cam 31 so as to pivot therewith.

In operation of the structure of FIGURE 3, prior to starting of the cold engine, the carburetor parts will be in the positions illustrated and cam 31 will be held in the cold starting position shown by reason of the frictional engagement with screw 29. Immediately upon starting of the engine without opening throttle 14 beyond the fast idle position illustrated in FIGURE 1, the force of the initial surge of inlet air against the unbalanced choke blade 12 will be resisted by spring finger 47 so as to limit the initial opening of blade-12 and to prevent stalling of the engine. The limited opening of choke 12 after the engine has started is permitted by movement of extension 37 along slot 38.

After the engine has been started and throttle 14 is opened to accelerate the engine and thereby to break the frictional engagement between screw 29 and cam 31, the choke 12 will be free to operate in accordance with the balance of the-forces exerted by thermostat spring 16, piston 41, counterweight 33 and the force of air pressure against the unbalanced choke blade 12. In the event that the throttle is returned tothe idle position prior to warming of the engine sufficiently to enable opening of choke blade 12 beyond the point whereat cam surface 39 engages screw 29, frictional contact between these elements will again hold cam 31 against pivotal movement. However in such an event, cam 31 will have been moved clockwise by operation of piston 41 approximately to the extent illustrated in FIGURE 2, so that the leverage of the projection 37 against spring finger 47 will be increased materially. Thus continued opening of choke blade 12 with increasing temperatures will be facilitated regardless of the resistance of spring 47.

In FIGURES 4 and 5, the basic carburetor structure is the same as. in FIGURES 1 and 2 with the exception that notch 39 is omitted and a tapered cam arm 49 keyed to choke shaft 13, a vertically shiftable cam rod 51 slidable in guide bushings 52 and terminating in an upper pointed end 50, and a rounded cam 53 keyed to throttle shaft 15 are added. By the structures shown, upon starting of the cold engine while the throttle is in the fast idle starting postion shown, the initial opening of choke blade 12 will be limited by contact between cam arm 49 and the pointed end 50 of rod 51. Thereafter, upon opening of throttle 14 to accelerate the engine, rod 59 will move downward by gravity to enable clockwise opening of choke 12 by the force of the air flow in conduit 11 until cam arm 49 is swung beyond the point of engagement with end 56 Thereafter choke valve 12 will be free to operate in the conventional manner. In the usual instance, piston 41 will be effective t3 maintain arm 4? clockwise beyond end 59 during cold i ling.

In the event the engine is turned off and allowed to cool, projection 49 will engage the lefthand side of point 50 as in FIGURE 5. Accordingly, inorder to return the throttle to the cold starting position of FIGURE 4, it is necessary first to depress rod 51 by opening throttle 14. Thermostat spring 16 will then return choke 12 to the. cold position, whereupon thr-ottle 14 may then be returned to the closed starting position of FIGURE 4.

FIGURES 6 and 7 illustrate another modification wherein the basic carburetor structure is the same as in FIGURES 1 and 2. In FIGURES 6 and7, the structure is adapted for starting with the throttle open, whereas in FIGURES 1 and 5, the structure shown are adapted for starting withthe throttle at the cold starting or fast idle positions illustrated. In FIGURES 6 and 7, notch 39 is eliminated. Also, instead of dog-leg link 43, a corresponding link 54 is provided with an upper end pivotally connected at 55 to the extension 45. The opposite end of link 54 is pivotally connected at 56 to one end of a short connecting link 57, the other end of. the latter link being pivotally connected at 58 to piston 51 to complete a toggle connection. A notch 59 is provided in the inner sidewall of cylinder 40 adjacent the latters left end to receive a depending projection 60 of link 54, FIGURE 6. The notch 59 is dimensioned so that immediately after starting the engine with the throttle 14 open, opening of choke valve 12 will be limited by engagement between projection 60 and the right edge of notch 59 to prevent stalling of the engine as described above.

In operation of the structure illustrated in FIGURES 6 and 7, throttle 14 is preferably open during starting. When the cold engine is initially started and while the throttle 14 is still open, limited opening of choke 12 is enabled by the lost motion of projection 60 in notch 59. When the throttle 14 is subsequently returned to the idle position in FIGURE 6, the loW pressure induced downstream of throttle 14 and conducted to the right side of piston 41 will exert sufficient force on the latter piston to pull projection 60 upwardly from notch 59 and enable operation of choke valve 12 in the customary manner. In this construction, when the engine is operated under load, the downward flow of air through conduit 11 will be sufiicient when the throttle 14 is open to maintain choke 12 open sufiiciently to prevent extension 60 from re-entering notch 59, regardless of the temperature condition of thermostat 16.

I claim:

ll. In a fuel charging device for an internal combustion engine, air inlet conduit means, unbalanced choke valve means in said conduit means susceptible to being urged to an open position by the force of air flowing in said inlet conduit means, thermostatic means responsive to decreasing temperature for yieldingly closing said choke valve means, fast idle cam means pivotal between cold and warm positions, a throttle valve in said conduit means, idle control means movable with said throttle valve and engageable with said cam means at the cold position upon closing movement of said throttle valve to limit said closing movement to a slightly open fast idle position and also to prevent pivoting of said cam means,

until said throttle valve is opened from said fast idle position, and restricting means to restrict the initial opening of said choke valve means to prevent a sudden flow of inlet air in said conduit means sufficie-nt to stall said engine immediately after the latter has begun to operate under its own power with said cam means at said cold position and said throttle valve at said fast idle position and to progressively facilitate opening of said choke valve means upon rotation of said cam means from said cold position toward said Warm position, said restricting means comprising a link pivotally connected at one end with choke valve means to move therewith, a lost motion slot extending in said cam means and having the other end of said link movably connected therein to engage said cam means at one end of said slot and pivot said cam means to said cold position upon closing of said choke valve means and to ride along said slot in guided movement in the direction from said one end upon opening of said choke valve means independently of said cam means, said one end of said slot extending transversely to the direction of force applied through said link to said other end thereof by force tending to open said choke valve means when said cam means is at said cold position and being rotatable into increasing alignment with the last named direction upon rotation of said cam means toward said warm position, thereby to enhance the leverage of force tending to resist said guided movement when said cam means is at said cold position and to decrease said leverage when said cam means is rotated toward said warm position, and means engageable with said link for yieldingly urging said other end of the latter to said one end of said slot and cooperating therewith to resist said guided movement with suffi cient force to prevent said sudden flow comprising resilient means carried by said cam means to pivot therewith.

2. In the combination according to claim 1, said resilient means being under tension yieldingly holding said other end of said link at said one end of said slot when said choke valve means is closed.

3. In the combination according to claim 2, said slot extending in said cam means arcuately from said one end thereof and partially around the pivot axis of said cam means in the direction of rotation of said cam means from its cold to its warm position.

References Cited by the Examiner UNITED STATES PATENTS 2,410,758 11/ 1946 Thompson 261-52 2,420,917 5/ 1947 Sutton et al. 26 1-52 2,540,607 2/1951 Boyce 26l52 2,762,354 9/ 1956 Winkler. 2,864,596 12/ 1958 Dermond. 2,901,229 8/1959 Sarto 26 152 2,998,233 8/1961 Marsee.

HARRY B. THORNTON, Primary Examiner.

HERBERT L. MARTIN, Examiner. 

1. IN A FUEL CHARGING DEVICE FOR AN INTERNAL COMBUSTION ENGINE, AIR INLET CONDUIT MEANS, UNBALANCED CHOKE VALVE MEANS IN SAID CONDUIT MEANS SUSCEPTIBLE TO BEING URGED TO AN OPEN POSITION BY THE FORCE OF AIR FLOWING IN SAID INLET CONDUIT MEANS, THERMOSTATIC MEANS RESPONSIVE TO DECREASING TEMPERATURE FOR YIELDINGLY CLOSING SAID CHOKE VALVE MEANS, FAST IDLE CAM MEANS PIVOTAL BETWEEN COLD AND WARM POSITIONS, A THROTTLE VALVE IN SAID CONDUIT MEANS, IDLE CONTROL MEANS MOVABLE WITH SAID THROTTLE VALVE AND ENGAGEABLE WITH SAID CAM MEANS OF THE COLD POSITION UPON CLOSING MOVEMENT OF SAID THROTTLE VALVE TO LIMIT SAID CLOSING MOVEMENT TO A SLIGHTLY OPEN FAST IDLE POSITION AND ALSO TO PREVENT PIVOTING OF SAID CAM MEANS UNTIL SAID THROTTLE VALVE IS OPENED FROM SAID FAST IDLE POSITION, AND RESTRICTING MEANS TO RESTRICT THE INITIAL OPENING OF SAID CHOKE VALVE MEANS TO PREVENT A SUDDEN FLOW OF INLET AIR IN SAID CONDUIT MEANS SUFFICIENT TO STALL SAID ENGINE IMMEDIATELY AFTER THE LATTER HAS BEGUN TO OPERATE UNDER ITS OWN POWER WITH SAID CAM MEANS AT SAID COLD POSITION AND SAID THROTTLE VALVE AT SAID FAST IDLE POSITION AND TO PROGRESSIVELY FACILITATE OPENING OF SAID CHOKE VALVE MEANS UPON ROTATION OF SAID CAM MEANS FROM SAID COLD POSITION TOWARD SAID WARM POSITION, SAID RESTRICTING MEANS COMPRISING A LINK PIVOTALLY CONNECTED AT ONE END WITH CHOKE VALVE MEANS TO MOVE THEREWITH, A LOST MOTION SLOT EXTENDING IN SAID CAM MEANS AND HAVING THE OTHER END OF SAID LINK MOVABLY CONNECTED THEREIN TO ENGAGE SAID CAM MEANS AT ONE END OF SAID SLOT AND PIVOT SAID CAM MEANS TO SAID COLD POSITION UPON CLOSING OF SAID CHOKE VALVE MEANS AND TO RIDE ALONG SAID SLOT IN GUIDED MOVEMENT IN THE DIRECTION FROM SAID ONE END UPON OPENING OF SAID CHOKE VALVE MEANS INDEPENDENTLY OF SAID CAM MEANS, SAID ONE END OF SAID SLOT EXTENDING TRANSVERSELY TO THE DIRECTION OF FORCE APPLIED THROUGH SAID LINK TO SAID OTHER END THEREOF BY FORCE TENDING TO OPEN SAID CHOKE VALVE MEANS WHEN SAID CAM MEANS IS AT SAID COLD POSITION AND BEING ROTATABLE INTO INCREASING ALIGNMENT WITH THE LAST NAMED DIRECTION UPON ROTATION OF SAID CAM MEANS TOWARD SAID WARM POSITION, THEREBY TO ENCHANCE THE LEVERAGE OF FORCE TENDING TO RESIST SAID GUIDED MOVEMENT WHEN SAID CAM MEANS IS AT SAID COLD POSITION AND TO DECREASE SAID LEVERAGE WHEN SAID CAM MEANS IS ROTATED TOWARD SAID WARM POSITION, AND MEANS ENGAGEABLE WITH SAID LINK FOR YIELDINGLY URGING SAID OTHER END OF THE LATTER TO SAID ONE END OF SAID SLOT AND COOPERATING THEREWITH TO RESIST SAID GUIDED MOVEMENT WITH SUFFICIENT FORCE TO PREVENT SAID SUDDEN FLOW COMPRISING RESILIENT MEANS CARRIED BY SAID CAM MEANS TO PIVOT THEREWITH. 